The proposal examines central nervous and sensory aspects of control of rhythmic behavior patterns, primarily in Limulus. The behavior patterns most studied are the respiratory rhythm, rhythmic feeding movements, and locomotion. For example, the respiratory rhythm; we are characterizing the motor output pattern underlying the behavior and are ascertaining the degree to which the pattern is centrally determined, and the degree to which it requires phasic sensory feedback. We then study the integrative mechanisms of central pattern generation and the interaction of these central mechanisms with sensory triggers and sensory feedback. BIBLIOGRAPHIC REFERENCES: Wyse, G.A. and C.H. Markey. 1975. The effect of forced cyclic gill movement on the respiratory rhythm of Limulus. Biol. Bull. 149: 452. Wyse, G.A. and C.H. Page. 1976. Sensory and central nervous control of gill ventilation in Limulus. Federation Proc. 35: 2007-2012.